This invention relates to a process for the production of flexible glass which has good strength, elasticity, wear resistance, thermostability, and will not support a flame. The glass may be produced as a solid or as a foamed product and utilized as flexible glass films, as coating agents, as adhesives, as binders, for molding useful products and as foam insulation.
It is well known in the arts that aqueous alkali metal silicates may be utilized as binders, adhesives, coating agents and films, but that it has many disadvantages because the products produced are very brittle and have poor strength properties. The novel products produced by the process of this invention are flexible, somewhat elastic and have good strength properties. It is known in the arts that the products produced from alkali metal silicate solution may be improved by the addition of polysilicate ions, but even with the addition of polysilicate ions, the products are still very brittle and are easily broken. On pages 122 and 123 of "The Chemistry of Silica" by Ralph K. Iler, published in 1979 by A. Wiley-Interscience Publication, New York, Iler discusses sodium silicate solutions used as adhesive and points out that the film formed by drying the water from the film of sodium silicate produces a film which is brittle and has micro-cracks that lower the strength of the dried film.
In the known processes to produce adhesive films, alkali metal silicate glass is made water soluble by utilizing boiling water or steam to break down the particles or large molecules of alkali metal silicates into smaller molecules which are water soluble. These smaller molecules of alkali metal silicates produce brittle films when dried. In the process of this invention, the particles or large molecules of alkali metal silicates are not broken down into small molecules, thereby producing strong, flexible films upon drying.
I have discovered that a strong, flexible glass product can be produced by mixing a powdered alkali metal silicate glass with an SiO.sub.2 :alkali metal oxide in a ratio of 2.0:1 to 3.9:1, preferable 2.0:1 to 3.2:1, and water forms an aqueous alkali metal silicate glass suspension. Then the suspension is dried to produce the flexible glass. 10 to 80 parts by weight of the alkali metal silicate glass are mixed with 50 to 100 parts by weight of water. The SiO.sub.2 :alkali metal oxide ratio of the aqueous alkali metal silicate glass suspension may be increased up to about 25:1 by the addition of oxidated silicon compounds such as hydrated silica, aqueous suspended silica, precipitated silica, fumed silica, silicic acid, polysilicic acid, etc. The amount of oxidated silicon compounds used is limited by the amount of water present.